Spinning young viscose



Patented June 3, 1 952 8 UNITED STATES PATENT OFFICE R r 7 2,598,834 I I SPINNING YOUNG .vrsoos'i:

George A. Richter, Jr., Springfield, Pa., assignor' to American Viscose Corporation, Wilmington, Del., a corporation of Delaware e No Drawing. Application April 28, 1951, Serial No. 223,661

This invention relates to artificial fibers of regenerated cellulose, and to processes for producing them from a young or unripened viscose.

In the normal production of fibers of regenerated cellulose from viscose, the viscose is stored for ripening or ageing, during which hydrolytic changes take place with gradual breaking away of the xanthate groups from the dissolved cellulose molecular chains, and conversion thereof into sulfur-containing by-products. The ripened viscose contains a relatively small number of xanthate groups chemically bound to the dissolved cellulose molecular chains and has a sodium chloride salt-test value of from 3 to 6, the salt-test value being, for a viscose of given composition, a relative measure of the number of xanthate groups present.

By the term young or unripened viscose as used herein is meant a viscose of given composition containing a relatively large number of i xanthate groups which are chemically bound to the dissolved cellulose molecular chains as indicated by a relatively high salt-test value. The young viscose may be a freshly prepared viscose which has not been stored for any appreciable time in excess of the period required to effect deaeration thereof prior to spinning, usually about 12 hours, a viscose to which an ageing or ripening retardant such as sodium sulfite has been added, or a ripened normally dexanthated viscose which has been re-xanthated prior to spinning by the addition of carbon disulfide directly 'to the viscose.

In any event, the young or unripened viscose which is formed into fibers in accordance with this invention has a sodium chloride salt-test value at least 1.19 times the percent sodium hydroxide in the viscose. Preferably, the salt test value is greater than 1.19 times the hydroxide content, being as high as 1.6 times the hydroxide content at near-optimum conditions. Stated broadly, the sodium chloride salt-test value for the young viscose is between 1.19 and 2 times the percent sodium hydroxide in the viscose, but is not usually higher than 18. Put another way, the salt-test value of the viscose is between 8 and 18 for viscose containing between 4 and 13 percent or higher of sodium hydroxide.

Many attempts have been made, in the past, to produce useful artificial fibers from young viscose or from normal viscose under conditions tending to retard the rate of dexanthation. However, it has not been possible to produce fibers having the combined properties of high tenacity and high wet and dry extensibility :by the methods proposed previously. Either the fibers have possessed acceptable tenacity at the expense of .ex-

Claims. (CI. 18-54) tensibility, or the conditions have been suchthat, after withdrawal from the spinning bath, the fibers could not be stretched to increase their tensile strength, without rupturing under comparatively light tensioning or stretching loads. Other methods proposed previously have involved the use of viscoses of abnormally high viscosity and poor dispersion. Such methods entail filtration and spinning difficulties which seriously hamper large scale operations and, moreover, the fibers obtained are not satisfactory. I It is an object of the present invention to pro vide a method of manufacturing novel artificial fibers from young viscose which are characterized by high tenacity coupled with high wet and dry extensibilities. Another object is to provide a method for producing the fibers from a young viscose of normal viscosity and dispersion. A particular object is to provide fibers of. regener-. ated cellulose which are useful for the production of tire cords or the like having an abnormally high flexing life.

It has been determined, in accordance with the present invention, that satisfactory fibers can only be obtained from a young viscose under special correlated conditions, based essentially upon the sodium hydroxide content of the viscose. Thus, it has been found that in order to obtain such fibers from a young viscose of any'given sodium hydroxide content it is necessary to employ spinning baths containing sulfuric acid in a concentration of from 0.5 to 0.7 times the sum of the weight percentage of the sodium hydroxide in the viscose and the salt-test value of the viscose and having a high total weight percentage of soluble metallic sulfate, not less. than 21% plus 0.66 times the weight percentage of sodium hydroxide, in the viscose, a portion of which must comprise a soluble sulfate of a polyvalent metal, The metallic sulfate content of the spinning bath may be made up of sodium sulfate and zinc sulfate, or an equivalent polyvalent metal sulfate, in varying relative proportions depending upon the composition of the viscose. In general, the relative proportion of sodium'sulfate to-zinc sulfate varies inversely with the causticlsoda-content of the viscose. Thus, when the caustic sb'da content of the viscose is relatively high, the'bath preferably contains a relatively high percentage of zinc sulfate, and a relatively low percentage of sodium sulfate, whereas when the causticasoda content of the viscose is relatively low,the bath preferably contains arelatively highipercentage of sodium sulfate and a relatively low percentage of zinc sulfate. In any event, under the preferred conditions of the invention, the sodium sulfate concentration in the bath is at least 18 and content-is that normally present in commercial viscoses, and is between 6 and 8%.

The following table is given to illustrate the relationship of the sodium hydroxide content of the young viscose (in per cent) to the constituents of the spinning bath, for the production of fibers or threads of exceptionally high tensile strength and extensibility from young viscoses of varying salt-test values within the range previously indicated.

Table 35 6 i figg Salt Test Percent Percent Percent Concin in Vis- Value H280 NMSO viscse 0050 I in bath in bath n bath 13 7. 5 15. 5 19. 5 9. 6 20. 0 7. 5 16. O 14. 3 9. 0 20. 0 10 7. 5 16. 0 14. 3 5. O 25. O a

7. 8 7. 3 12. O 12. O 5. O 26. O 5. 0 8. 0 11. O 9 0 3. O 24. 0 4. O 8. O 8. O 8. 0 2. 0 23. 0

Although, as previously stated, and as is evident from the foregoing table, some variation is permissable in the concentration of sulfuric acid,

sodium sulfate, and zinc sulfate or the like in the bath, with variation in the percent sodium hydroxide in the viscose, it has been found that if the sulfuric acid is present in the bath in a concentration of less than 0.5 to 0.7 times the sum of the weight percentage of the sodium hydroxide and the salt test, and the total weight percentage ofsoluble metallic sulfate concentration of the bath, atleast-a portion of which is a soluble polyvalent' metal sulfate, is less than 21 plus 0.66 times the weight percentage of sodium hydroxide in the viscose, the fibers obtained by spinning the young viscose are filled with small voids or cracks which weaken the threads and impart a milky young viscose. in accordance with this. invention even under very high magnification. The present invention does not involve any departure from standard practice in connection with adjustment of the viscosity of. the viscose or dispersion of the cellulose xanthate therein, 'or in the manner in which the fibers are handled. The viscoseis spunat normal viscosity 1. e. at a viscosity between 30 and 60 pulses. The bath may be maintained at the usual temperatures, and the immersion length of the fibers in the bath is the same, as the immersion length for fibers obtained by spinning a normal viscose under normal conditions by the wet spinning method.

Aftertheir withdrawal from the spinning bath,

' theifibers are subjected to stretching. Here the fibers exhibit 'a remarkabledifference from the fibers obtained from so-called normal viscose, in that they areca'pable'of accepting a stretch which is-f-rom 20'to 30% greater than the stretch which fibers from normal viscose will accept without rupture. Forany given percent stretch, the new fibrs have a higher strength and higher ex-' tensibilitythan do normal fibers from normally matured viscose which have been given the same stretch. The new fibers may, if desired, be given a stretch of from '75 to of their length. The stretched fibers have a dry tenacity substantially greater than 3 gins/denier and a wet tenacity which is also excellent, generally about 2.5 gins/denier. Surprisingly, even When the fibers are given the high stretch which they are capable of accepting, their extensibility is at least as high as, and in many cases higher than, the extensibility of conventional regenerated cellulose fibers. The new fibers have an elongation at breaking point of at least 14%.

The reason for the remarkable ability of the present fibers to withstand stretching up to 110% of their length without rupture is not entirely clear. However, it appears that the presence of the soluble polyvalent metal sulfate in the bath exerts an influence upon the fibers in this respect. It has been determined that the presence of the zinc sulfate, or equivalent, in the spinning bath is essential for the production of strong, extensible fibers from young viscose. Probably, the polyvalent metal sulfate exerts a two-fold ellect; Thus, undoubtedly, it has some dehydrating action on the viscose, serving to assist in the coagulation of the cellulose xanthate from the viscose solution. Additionally, there is some evidence that when zinc sulfate or the like is present in a spinning bath it temporarily cross-links the cellulose molecular chains through the xanthate' groups by means of ionic bridges, thus preventing the rotation of the cellulose chains into preferred positions of crystallinity during the processof coagulation, and resulting in fibers which contain a large number of relatively small crystalline regions with simultaneous increase in the amount of amorphous cellulose in the fibers or threads. The xanthate groups are subsequently hydrolyzed from the cellulose molecular chains forming regenerated cellulose yarn. Since the cellulose'in young viscose is more highly xanthated than the cellulose in a normal ripened or aged viscose, that is a viscose in which only a'relativelyfewxanthate groups are chemically bound to the dissolved cellulose molecular chains, it is probable that, in the case of the young viscose, a greater number of zinc ionic cross-links are formed during the spinning, so that even smaller crystalline regions are formed than has been possible hitherto. The smaller crystalline regions and the increase in the number of such regions, together with the increase in amorphous cellulose present in the fibers, would account for the ability of the fibers to withstand the extremely high stretch to which the fibers are subjected in accordance with this invention.

Preferably, the polyvalent metal sulfate used is zinc sulfate, but soluble sulfates of other polyvalent metals may be substituted for, or used in combination with, the zinc sulfate, such as the sulfates of iron, magnesium, chromium, cadmium, manganese, nickel, and aluminum. Whichever polyvalent metal isselected, the total weight percentage of metallic sulfate of the bath must be high, asv stated, not less than '21 plus 0.66 times the weight percentage of sodium hydroxide in the viscose in order toinsurea strong dehydrating action of the bath for efiecting coagulation of the highly solvated cellulosexanthate present in the young viscose.

Obviously, different types of systems may be employed. to effectstretching of thefibers. For instance;- the. fibers or thread. may be passed" between driven godets rotating at different peripheral speeds, or stretching may be effected by means of stepped rollers, or by means of freely rotatable rollers of different size. In a continuous spinning system, stretching may be effected as the threads travel over a thread-storing, thread-advancing reel. The threads may be, and preferably are, subjected to the action of a plasticizing agent, such as a hot water or steam cascade, concomittantly with their stretching. Howeve the use of such stretching aids is optional. 7

The highly stretched young viscose in accordance with the invention show, on X-ray examination, a unique crystalline structure by which they are fundamentally distinguished'from usual regenerated'cellulose fibers" from viscose. Thus, the fibers are more amorphous than the conventional fibers and, at the same time, the small crystalline micelles are more a highly oriented in a direction parallel to the long axis of the fiber. The more amorphous structure of the threads produced as described herein is indicated, also, by controlled hydrolysis studies.

The fibers produced in accordance with the invention are useful, for all of the purposes to which'such fibers are usually put. However, because of their very high tenacity coupled with high extensibility, the fibers are particularly well suited for use in tire cords. by plying together yarns spun from young viscose in accordance with this invention have a tensile strength, after conditioning at 58% relative humidity, of at least 3 gms./denier, an extensibility of at least 8%, and a flexing life of at least 50,000. cycles as measured by the standard Firestone test. Tire cords have been prepared, in accordance with this invention, having a flexing life corresponding to a Firestone rating of as high as 2.6. (The Firestone rating is based upon a normal tire cord which has a flexing lifev of 32,000 cycles and a rating of 1. Tire cords comprising the fibers spun from a young viscose in accordance with this invention may be said, therefore, to have a flexing life of as high as 84,600 cycles.)

The maximum limit for the acid concentration in the spinning bath when spinning a young viscose in accordance with this invention also depends upon the type of viscose under consideration. In the present case, the maximum allowable acid concentration in the bath is that concentration above which excessive cellulose degradation occurs and is, in general, about 2.0 times the percentage caustic soda in the young viscose.

The maximum permissible concentrations of sodium sulfate and zinc sulfate are determined by the solubility of these salts in sulfuric acid. In general, the maximum total concentration of zinc sulfate and sodium sulfate, taken together, which can be dissolved in sulfuric acid of the concentration used when spinning in accordance with this inventionis about 32%.

' .The conditions permit of normal spinning speeds, generally, the spinning speed is about 60 meters per minute.

The following examples will serve to illustrate the present invention. All concentrations are calculated as parts by weight of the viscose, or of the bath.

- Example I A viscose solution having a composition of 7.5 cellulose and 13% hydroxide and a sodium fibers obtained from Tire cords prepared through spinnerets to forma thread of .40 filaments and 150 denier. The thread was passed through a bath containing, 19.3% sulfuricacid, 9.6% zinc sulfate and 20% sodium sulfate. The bath temperature was C. and the length of immersion of the thread in the bath was 24 inches. After passing through the bath, the thread was stretched 110 in a hot water cascade between two godets, after which it was passed through a funnel into a spinning box revolving at a speed of 7000 R. P. M. The delivery speed of the thread to the box was meters per minute. The yarn was washed, desulfided, bleached, and a softfinish was applied. The propertiesof the resultingthread were as follows:

' Conditioned at 58% R. H. Wet

Tensile Strength I gms/denier Tensile Strength, gmsJdenier Elongation Elongation (Per Cent).

(Per Cent) Example II A viscose solution having a composition of 7.5% cellulose and 10 sodium hydroxide and a sodium chloride salt-test value of about 16 was extruded through spinneretsto form a thread of 40 filaments and 150 denier. The thread was passed through a bath containing 13.6% sulfuric acid.

8.8% zinc sulfate and 20% sodium sulfate. The bath temperature was 50 C. and the length of immersion of the thread in the bath was 24 inches." 'After' passing through the bath the thread was stretched ina hot water cascade between two godets, after which it was collected and finished as in Example I. The properties of Example III A viscose solution having a composition of 7.5% cellulose and 10% sodium hydroxide and a sodium chloride salt-test value of 16.0 was extruded through spinnerets to form a thread of 490 filaments and 1200 denier. The thread was passed through a bath containing 14.3% sulfuric acid, 9% zinc sulfate and 20% sodium sulfate. The bath temperature was 50 C. and the length of immersion of the thread in the bath was 44 inches. After passing through the bath, the thread was stretched in a hot water cascade between two godets, after which it was collected and finished as in Example II. The properties of the resulting thread were as follows:

The thread, afterbeing finished and dried, was stretched still further on a conventional Slasher to produce a product with an extensibility of 10.2%. This thread was then made into a two- 'strand the cord of the construction 14/l1 (14 turns/in. Z-twist on the single yarn, 11 /2 A viscose solution having a composition of 7.3% cellulose and 7.8% sodium hydroxide and a sodium chloride salt-test value of 11.7 was extruded through spinnerets toform a thread of 490 filaments and 1200 denier. through a' bath containing 12.1% sulfuric acid, 5.0% zinc sulfate and 26.5%sodium sulfate. The

bath temperature was 50 C. and the length of After passing through.

immersion was 34-inches. the bath, the thread was stretched 110% in a hot Water cascade between two godets, after which it was collected and finished as in I. The properties of the resulting thread were as follows:

\ Conditioned at 58% R. H. Wet

Tensile Tensile Strength, Strength, gins/denier gins/denier The thread, after being finished and dried, was

stretched still further on a conventional slasher to produce a product with an extensibility of 10.2%. The thread was then made into a two strand tire cord of the construction 14/11 The properties of the cord are as follows:

Conditioned at 58% R. 1-1.

Oven Dry Firestone rat ngrlexrng life Tensile Strength, gins/denier Tensile Strength, gins/denier Elongation Elongation (Per Cent) (Per Cent) Example V A viscose containing 8% cel1ulose,.5% sodium length was 24 inches, the spinning speed 60 meter/minute. After withdrawal from the bath, the thread was stretched 80% between two godets. The yarn was washed, desulfided,

' bleached and given a soft finish. It had the following properties:

The thread was passed Oonditioned at 58% R. H. 7 Wet Tensile Tensile ggggsi; Strength, bflity Strength, Bflity gmsjdenier (Per Cent) gins/den er (Per Cent) The thread was made into a two-strand tire cord as in Example III. The cord had the following properties:

Conditioned at 58% R. H. Oven Dry Tensile Tensile Firestone Strength, gg igg, Strength, g g iggf rating" gins/denier grns denier. Flcxin'g life At 10 lbs. 103a.

Example VI A viscose containing 8% cellulose, 4% sodium hydroxide and 38% CS2, and having a sodium chloride "salt-test value of 6.7 was extruded through spinnerets into a bath containing 7.2% sulfuric acid, 2.2% zinc sulfate, and 722.3% sodium sulfate, at 55 C., to form a 490 filament.

1200 denier thread, the immersion distance -being 14 inches. The thread'was withdrawn from the. bath, stretched 757% between godets, collected and finished as in Example III. The properties'of this thread were asfollows:

' Conditioned at 58% R. H. Wet

. Brcakin Breakin Tglslle Extensi- T611511? Extensi- Strength. bimy Strength, gals/denier (Pele e116) gins/denier (Pen Ceyfit) limited except as defined by-thespirit and scope V of the appended claims.

I claim:

1. A method of makingfrom viscose regenerated cellulosefibers capable of accepting a stretch of from.'75 to 110% which consists of the steps of extruding viscose containing-cellulose x'anthate as its. sole xanthate component, of .normal viscosity andnormal cellulose content, andhaving a sodium hydroxide content of from 4 to 13% and a sodium chloride salt-test value which: is between 1.19 and 2 times the weight percentage of sodium hydroxide in the viscose and not less than 8 nor greater than 18, into a coagulating and regenerating bath maintained at a temperature of to C. and comprising essentially an aqueous solution of sulfuric acid and. soluble metallic sulfate, the sulfuric acid being present in a concentration of from 0.5 to 0.7 times the sumrof the weight percentage of sodium hydroxide in" the "viscose and the sodium chloride salt-test value of'the'viscose; and the-soluble metallic sul fate being present in a total concentration of at least 21% plus 0.66 times the weight percentage of sodium hydroxide in the viscose, the metallic sulfate consisting of at least 18% sodium sulfate and at least 1% of a polyvalent metal sulfate, to form fibers, Withdrawing the fibers from the bath, and stretching the fibers.

2. A method as in claim 1, wherein viscose containing about 7.5% cellulose and about 13% sodium hydroxide, and having a salt-test value of about 15.5 is extruded into a coagulating and regenerating bath comprising essentially an aqueous solution of about 19.3% sulfuric acid, about 20% sodium sulfate, and about 9.6% zinc sulfate.

3. A method as in claim 1, wherein viscose containing about 7.5% cellulose and about 10% sodium hydroxide, and having a salt-test value of about 16 is extruded into a coagulating and regenerating bath comprising essentially an aqueous solution of about 13.6% sulfuric acid, about 20% sodium sulfate, and about 8.8% zinc sulfate.

4. A method as in claim 1, wherein viscose containing about 7.3% cellulose and about 7.8% sodium hydroxide, and having a salt-test value of about 11.7 is extruded into a coagulating and regenerating bath comprising essentially an aqueous solution of about 12.1% sulfuric acid, about 26.5% sodium sulfate, and about 5% zinc sulfate.

5. A method of making tire cords which comprises extruding viscose containing cellulose xanthate as its sole xanthate component, of normal viscosity and normal cellulose content and having a sodium hydroxide content of from 4 to 13% and a sodium chloride salt-test value equal to at least 1.19 times the weight percentage of sodium hydroxide in the viscose, the salt-test being, in

any case, not less than 8 nor greater than 18,

into a coagulating and regenerating bath maintained at a temperature of 45 to 50 C. and comprising essentially an aqueous solution of sulfuric acid and soluble metallic sulfate, the sulfuric acid being present in a concentration of from 0.5 to 0.7 times the sum of the weight percentage of sodium hydroxide in the viscose and the salttest value of the viscose, and the soluble metallic sulfate being present in a total concentration of at least 21% plus 0.66 times the weight percentage of sodium hydroxide in the viscose, the soluble metallic sulfate consisting of at least 18% sodium sulfate and at least 1% of a polyvalent metal sulfate, to form fibers, withdrawing the fibers from the bath, stretching the fibers, forming the fibers into a yarn, after-treating the yarn, afterstretching the yarn, and plying at least two of the yarns together to form a cord.

6. A method as in claim 5, wherein viscose containing about 7.5% cellulose and about 13% sodium hydroxide, and having a salt-test value of about 15.5 is extruded into a coagulating and regenerating bath comprising essentially an aqueous solution of about 19.3% sulfuric acid, about 20% sodium sulfate, and about 9.6 zinc sulfate.

7. A method as in claim 5, wherein viscose containing about 7.5% cellulose and about 10% sodium hydroxide, and having a salt-test value of about 16 is extruded into a coagulating and regenerating bath comprising essentially an aqueous solution of about 13.6% sulfuric acid, about 20% sodium sulfate, and about 8.8% zinc sulfate.

8. A method as in claim 5, wherein viscose containing about 7.3% cellulose and about 7.8% sodium hydroxide, and having a salt-test value of about 11.7 is extruded into a coagulating and regenerating bath comprising essentially an aqueous solution of about 12.1% sulfuric acid. about 26.5% sodium sulfate, and about 5% zinc sulfate.

9. A method as in claim 1, wherein the fibers are given a stretch of from to 10. A method as in claim 5, wherein the fibers are given a stretch of from 75% to 110%.

GEORGE A. RICHTER, JR.

N 0 references cited. 

1. A METHOD OF MAKING FROM VISCOSE REGENERATED CELLULOSE FIBERS CAPABLE OF ACCEPTING A STRETCH OF FROM 75 TO 110% WHICH CONSISTS OF THE STEPS OF EXTRUDING VISCOSE CONTAINING CELLULOSE XANTHATE AS ITS SOLE XANTHATE COMPONENT, OF NORMAL VISCOSITY AND NORMAL CELLULOSE CONTENT, AND HAVING A SODIUM HYDROXIDE CONTENT OF FROM 4 TO 13% AND A SODIUM CHLORIDE SALT-TEST VALUE WHICH IS BETWEEN 1.19 AND 2 TIMES THE WEIGHT PERCENTAGE OF SODIUM HYDROXIDE IN THE VICSOCE AND NOT LESS THAN 8 NOR GREATER THAN 18, INTO A COAGULATING AND REGENERATING BATH MAINTAINED AT A TEMPERATURE OF 45 TO 50* C. AND COMPRISING ESSENTIALLY AN AQUEOUS SOLUTION OF SULFURIC ACID AND SOLUBLE METALLIC SULFATE, THE SULFURIC ACID BEING PRESENT IN A CONCENTRATON OF FROM 0.5 TO 0.7 TIMES THE SUM OF THE WEIGHT PERCENTAGE OF SODIUM HYDROXIDE IN THE VISCOSE AND THE SODIUM CHLORIDE SALT-TEST VALUE OF THE VISCOSE, AND THE SOLUBLE METALLIC SULFATE BEING PRESENT IN A TOTAL CONCENTRATION OF AT LEAST 21% PLUS 0.66 TIMES THE WEIGHT PERCENTAGE OF SODIUM HYDROXIDE IN THE VISCOSE, THE METALLIC SULFATE CONSISTING OF AT LEAST 18% SODIUM SULFATE AND AT LEAST 1% OF A POLYVALENT METAL SULFATE, TO FORM FIBERS, WITHDRAWING THE FIBERS FROM THE BATH, AND STRETCHING THE FIBERS. 